1. Field of the Invention
The present invention relates to the measurement and testing of cement, and particularly to a method of obtaining simulated pore water from cement in sufficient quantities for extraction and analysis thereof.
2. Description of the Related Art
Concrete is prepared from a mixture of cement, water, and an aggregate (sand, stone, gravel, etc.), which is generally assumed to be inert. When first mixed, the materials form a plastic-like mass that can be formed into the desired shape by a mold or the like. As the material cures, a chemical reaction called hydration takes place between the cement and the water, causing the concrete to harden into a stone-like condition in which the hydrated cement holds the aggregate in place. The properties of the resulting concrete are affected by the water-to-cement (W/C) ratio, the composition of the cement, and other factors. Sometimes an admixture or additive is added to the mix to accelerate or retard the initial set of the concrete, to improve workability, to reduce water requirements, to increase strength, or to otherwise alter the properties of the concrete. Admixtures may include accelerators, retardants, air-entraining agents, workability agents, dampproofing and permeability reducing agents, pozzolans, color pigments, and other additives.
Although the vast majority of the water is consumed by hydration or evaporation as the mix hardens or cures, concrete is porous, and a small amount of the water, referred to as “pore water”, may be entrapped in pores or channels in the concrete. It is believed that the pore water may produce undesirable effects affecting the properties of the concrete. Thus, the pore water may cause leaching of salts, corrosion of steel reinforcement embedded in the concrete, or other effects diminishing the strength, durability, permeability, or other properties of the concrete. The water in the initial mix or cement paste is also referred to as pore water, being the precursor of pore water found in the hardened concrete.
Therefore, part of the testing of concrete involves the analysis of pore water for pH, salt content, etc. Conventional methods for obtaining pore water include high-speed centrifuging of the cement paste when it is in the plastic state, or crushing the paste and using a press if the paste has hardened too much for centrifuging. However, the quantity of pore water obtained by such methods is always small, and particularly when the water-to-cement ratio is low, the quantity of pore water obtained may be too small to perform the desired analysis.
Thus, a method of obtaining simulated pore water solving the aforementioned problems is desired.